Improvements of mode converters for low-power excitation of gyrotron-type modes

Pereyaslavets, M.; Braz, O.; Kern, Stefan; Losert, M.; Möbius, A.; Thumm, M.

doi:10.1080/002072197136291

Cited by 18 publications

(10 citation statements)

References 7 publications

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“…As in coaxial-cavity gyrotrons, a metallic insert is used to assist the easier excitation of the desired mode [7,8]. The outer wall of the cavity is perforated in the midsection area [9], so that the wave beam can couple to the resonant mode in the cavity. The correct TEm,n mode, where m is the azimuthal and n the radial index, is excited depending on the dimensions, the frequency and the irradiation of the midsection.…”

Section: Advanced Measurement Setupmentioning

confidence: 99%

Computer-Controlled Test System for the Excitation of Very High-Order Modes in Highly Oversized Waveguides

Ruess

Avramidis

Gantenbein

et al. 2019

J Infrared Milli Terahz Waves

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The generation of a specific high order mode with excellent mode purity in a highly oversized cylindrical waveguide is mandatorily required for the verification of high power components at sub-THz frequencies. An example is the verification of quasi-optical mode conversion and output systems for fusion gyrotrons. A rotating high order mode can be excited by taking a low power RF source (e.g. RF network analyser) and by injecting the RF power via a horn antenna into a specific adjustable quasi-optical setup, the so-called mode generator. The manual adjustment of the mode generator is typically very time consuming. An automatized adjustment using intelligent algorithms can solve this problem. In the present work the intelligent algorithms consist of five different mode evaluation techniques to determine the azimuthal and radial mode indices, the quality factor, the scalar mode content and the amount of the counter-rotating mode. Here, the implemented algorithms, the design of the computer-controlled mechanical adjustment and test results are presented. The new system is benchmarked using an existing TE28,8 mode cavity operating at 140 GHz. In addition, the repeatability of the algorithms has been proven by measuring a newly designed TE28,10 mode generator cavity. Using the described advanced mode generator system, the quality of the excited modes has been significantly improved and the time for the proper adjustment has been reduced by at least a factor of 10.

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Section: Advanced Measurement Setupmentioning

confidence: 99%

Computer-Controlled Test System for the Excitation of Very High-Order Modes in Highly Oversized Waveguides

Ruess

Avramidis

Gantenbein

et al. 2019

J Infrared Milli Terahz Waves

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“…For easier excitation of the mode, a coaxial cavity is used. The cavity wall is perforated so that the wave can propagate from the quasi-parabolic mirror into the cavity [14].…”

Section: Mode Generatormentioning

confidence: 99%

Studies towards an upgraded 1.5 MW gyrotron for W7-X

et al. 2019

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Studies towards a 1.5 MW, 140 GHz CW gyrotron, with the capability of MW-class operation also at 175 GHz, are ongoing at Karlsruhe Institute of Technology in view of a possible future upgrade of the ECRH system of the stellarator W7-X. The upgrade of the existing 1.0 MW, 140 GHz European gyrotron for W7-X has been chosen as a development path. Detailed designs of the cavity, the non-linear uptaper, and the quasi-optical launcher for the upgraded gyrotron have been obtained and have been validated numerically. In parallel, a mode generator, intended for low-power tests of the quasi-optical mode converter system of the upgraded gyrotron, has been designed, manufactured, and successfully tested.

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“…The T. Ruess 1 quasi-parabolic mirror focuses the wave to the caustic of the desired mode in the mode generator cavity. The perforated cavity wall is translucent that the wave can couple into the cavity [6]. The profile of the mode generator cavity is designed using a scattering matrix code [7].…”

Section: Mode Generator Setupmentioning

confidence: 99%

Automated Generation of High-Order Modes for Tests of Quasi-Optical Systems of Gyrotrons for W7-X Stellarator

Ruess

Avramidis

Gantenbein

et al. 2019

2019 12th German Microwave Conference (GeMiC)

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A test system for the verification of the quasioptical converter system is vital in the gyrotron development. For this reason, an automated measurement setup has been developed and is benchmarked with the TE 28,8 mode operating in the cavities of the gyrotrons of W7-X with a high purity of about 95 % and a counter-rotating amount of about 0.3 %. The time duration for the mode generator adjustment has been reduced to two days for this mode. After a successful mode excitation, the quasi-optical mode converter, consisting of a launcher and three mirrors, is measured having a vectorial Gaussian mode content of 97 %.

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Improvements of mode converters for low-power excitation of gyrotron-type modes

Cited by 18 publications

References 7 publications

Computer-Controlled Test System for the Excitation of Very High-Order Modes in Highly Oversized Waveguides

Computer-Controlled Test System for the Excitation of Very High-Order Modes in Highly Oversized Waveguides

Studies towards an upgraded 1.5 MW gyrotron for W7-X

Automated Generation of High-Order Modes for Tests of Quasi-Optical Systems of Gyrotrons for W7-X Stellarator

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